Triangle ABC is isosceles.

Triangle A B C is shown. The lengths of sides A C and A B are congruent. Angle C A B is (x + 5) degrees. Angle A B C is (3 x) degrees.

What is the measure of angle C?

25°
30°
60°
75°

75°

Step-by-step explanation:

Using the Base Angles Theorem, we can conclude that <ABC and <ACB are congruent. The angles of a triangle add up to 180 degrees so we can write this equation to solve for x:

x + 5 + 3x + 3x = 180

simplify

7x + 5 = 180

subtract 5 from both sides

7x = 175

divide each side by 7

x = 25

plug 25 in for x to find the angle measure

3(25) = 75